#include "asm/system.h"
#include "linux/kernel.h"
#include "string.h"

#define is_digit(c) ((c) >= '0' && (c) <= '9')

static int skip_atoi(const char** s)
{
    int i = 0;
    while (is_digit(**s))
    {
        i = i * 10 + *((*s)++) - '0';
    }
    return i;
}

#define ZEROPAD	1		/* pad with zero */
#define SIGN	2		/* unsigned/signed long */
#define PLUS	4		/* show plus */
#define SPACE	8		/* space if plus */
#define LEFT	16		/* left justified */
#define SPECIAL	32		/* 0x */
#define SMALL	64		/* use 'abcdef' instead of 'ABCDEF' */

// 这个宏的意思是对于输入的整数n，除以base，商放在n中，余数返回
#define do_div(n,base) ({ \
int __res; \
__asm__("div %4":"=a" (n),"=d" (__res):"0" (n),"1" (0),"r" (base)); \
__res; })

static char *number(char *str, long num, int base, int size, int precision, int type)
{
    char c, sign, tmp[36];
    const char *digits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    int i;

    if (type & SMALL)
    {
        digits = "0123456789abcdefghijklmnopqrstuvwxyz";
    }
    if (type & LEFT)
    {
        type &= ~ZEROPAD;
    }
    if (base < 2 || base > 36)
    {
        return 0;
    }
    c = (type & ZEROPAD) ? '0' : ' ';
    sign = 0;
    if (type & SIGN)
    {
        if (num < 0)
        {
            sign = '-';
            num = -num;
            size--;
        }
        else if (type & PLUS)
        {
            sign = '+';
            size--;
        }
        else if (type & SPACE)
        {
            sign = ' ';
            size--;
        }
    }
    if (type & SPECIAL)
    {
        if (base == 16)
        {
            size -= 2;
        }
        else if (base == 8)
        {
            size--;
        }
    }
    i = 0;
    if (num == 0)
    {
        tmp[i++] = '0';
    }
    else
    {
        while (num != 0)
        {
            tmp[i++] = digits[do_div(num, base)];
        }
    }
    if (i > precision)
    {
        precision = i;
    }
    size -= precision;
    if (!(type & (ZEROPAD + LEFT)))
    {
        while (size-- > 0)
        {
            *str++ = ' ';
        }
    }
    if (sign)
    {
        *str++ = sign;
    }
    if (type & SPECIAL)
    {
        if (base == 8)
        {
            *str++ = '0';
        }
        else if (base == 16)
        {
            *str++ = '0';
            *str++ = digits[33];
        }
    }
    if (!(type & LEFT))
    {
        while (size-- > 0)
        {
            *str++ = c;
        }
    }
    while (i < precision--)
    {
        *str++ = '0';
    }
    while (i-- > 0)
    {
        *str++ = tmp[i];
    }
    while (size-- > 0)
    {
        *str++ = ' ';
    }
    return str;
}

int vsprintf(char *buf, const char *fmt, va_list args)
{
    int len;
    unsigned long num;
    int i, base;
    char *str;
    const char *s;
    int *ip;

    int flags;		/* flags to number() */

    int field_width;	/* width of output field */
    int precision;		/* min. # of digits for integers; max
                 number of chars for from string */
    int qualifier;		/* 'h', 'l', or 'L' for integer fields */

    for (str = buf; *fmt; fmt++)
    {
        if (*fmt != '%')
        {
            *str++ = *fmt;
            continue;
        }

        /* process flags */
        flags = 0;
    repeat:
        fmt++;		/* this also skips first '%' */
        switch (*fmt)
        {
        case '-':
            flags |= LEFT;
            goto repeat;
        case '+':
            flags |= PLUS;
            goto repeat;
        case ' ':
            flags |= SPACE;
            goto repeat;
        case '#':
            flags |= SPECIAL;
            goto repeat;
        case '0':
            flags |= ZEROPAD;
            goto repeat;
        }

        /* get field width */
        field_width = -1;
        if (is_digit(*fmt))
        {
            field_width = skip_atoi(&fmt);
        }
        else if (*fmt == '*')
        {
            /* it's the next argument */
            field_width = va_arg(args, int);
            if (field_width < 0)
            {
                flags |= LEFT;
                field_width = -field_width;
            }
        }

        /* get the precision */
        precision = -1;
        if (*fmt == '.')
        {
            fmt++;		/* skip '.' */
            if (is_digit(*fmt))
            {
                precision = skip_atoi(&fmt);
            }
            else if (*fmt == '*')
            {
                /* it's the next argument */
                precision = va_arg(args, int);
            }
            if (precision < 0)
            {
                precision = 0;
            }
        }

        /* get the conversion qualifier */
        qualifier = -1;
        if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L')
        {
            qualifier = *fmt;
            fmt++;
        }

        /* default base */
        switch (*fmt)
        {
        case 'c':
            if (!(flags & LEFT))
            {
                while (--field_width > 0)
                {
                    *str++ = ' ';
                }
            }
            *str++ = (unsigned char) va_arg(args, int);
            while (--field_width > 0)
            {
                *str++ = ' ';
            }
            break;
        case 's':
            s = va_arg(args, char *);
            len = strlen(s);
            if (precision < 0)
            {
                precision = len;
            }
            else if (len > precision)
            {
                len = precision;
            }

            if (!(flags & LEFT))
            {
                while (len < field_width--)
                {
                    *str++ = ' ';
                }
            }
            for (i = 0; i < len; i++)
            {
                *str++ = *s++;
            }
            while (len < field_width--)
            {
                *str++ = ' ';
            }
            break;
        case 'o':
            str = number(str, va_arg(args, unsigned long), 8,
                             field_width, precision, flags);
            break;
        case 'p':
            if (field_width == -1)
            {
                field_width = 8;
                flags |= ZEROPAD;
            }
            str = number(str,
                             (unsigned long) va_arg(args, void *), 16,
                             field_width, precision, flags);
            break;
        case 'x':
            flags |= SMALL;
        case 'X':
            str = number(str, va_arg(args, unsigned long), 16,
                             field_width, precision, flags);
            break;
        case 'd':
        case 'i':
            flags |= SIGN;
        case 'u':
            str = number(str, va_arg(args, unsigned long), 10,
                             field_width, precision, flags);
            break;
        case 'n':
            ip = va_arg(args, int *);
            *ip = (str - buf);
            break;
        default:
            if (*fmt != '%')
            {
                *str++ = '%';
            }
            if (*fmt)
            {
                *str++ = *fmt;
            }
            else
            {
                fmt--;
            }
            break;
        }
    }
    *str = '\0';
    return str - buf;
}